This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined below, prior to the claims.
In a cellular communication system, multiple users attempt to simultaneously access a radio access network (RAN) wirelessly via their user equipment (UE). The RAN for an LTE system is implemented in an eNB. Uplink and downlink user data is passed between the RAN and the UE, and the RAN needs to transmit the uplink and/or downlink data assignments via the PDCCH channel.
The PDCCH comprises a limited number of control channel elements (CCEs) which may be configured in groups of 1, 2, 4, or 8 as a function of the coding rate that is needed for reliable transmission to the UE. Using more CCEs results in more reliable transmission (e.g., lower coding rate) but consumes more capacity. The total number of PDCCH CCEs available depends on the system bandwidth and the number of symbols configured for use by the PDCCH, where the maximum number is limited by the LTE standard.
Since both uplink and downlink transmissions require use of the PDCCH, and since the capacity of the PDCCH is limited, the PDCCH is a critical capacity bottleneck within the LTE system. This fact is well recognized within the cellular industry.
Some customers of cellular equipment demand very high LTE-connected UE capacity, with customers demanding 1000 or more RRC-connected UEs per cell/carrier. Work is being performed on features to increase the connected UE capacity in current and future LTE releases to meet these demands.
As the connected UE capacity increases, the PDCCH may quickly become a significant capacity and performance bottleneck. This is due to the need to schedule, using the PDCCH, both user data (DTCH) as well as periodic control information (DCCH, CCCH)—such as status PDUs, time alignment commands, buffer status reports, and other information—to each connected UE, where each of these scheduling events to each connected UE requires PDCCH capacity.
It would be beneficial to improve use of PDCCH as the connected UE capacity increases in a cell, e.g., to avoid or lessen the severity of PDCCH capacity bottlenecks.